For the treatment of elongate objects like free tensioned support cables, e.g., of diagonal cable or vertical cable bridges, cable trucks have been used. They are operated like a cable car, and are occupied by one or two workers who perform the surface treatment of the cable more or less manually. The cable to be treated is stationary while a second cable moves and serves the purpose of propulsion of the cable truck.
The treatment of such cables usually comprises cable cleaning including descaling and/or stripping off an old coating, cable painting includes the application of a coating material (paint), and, sometimes, prior to the painting, cable caulking. During cable caulking, which is performed prior to a final application of coating or painting layer, a coating or sealing material is forced down into the voids and cracks of a wire rope so that all gaps between the strands and wires are caulked shut.
Therefore, subsequent coating layers can be applied to a surface that is fairly smooth and uniform. Cable painting without prior cable caulking usually protects only most of the exterior but not those areas which are in gaps between the bundles. Such an incomplete coating may allow water intrusion extending inside of the cable.
For cleaning and painting mobile units are known which are propelled along a cable to be treated.
U.S. Pat. No. 4,169,427 A1 discloses a cable unit comprising a chamber adapted to surround a section of the cable to be cleaned, a plurality of outlets located within the chamber through which jets of high pressure fluid are directed onto the surface of the cable and a mechanism for withdrawing fluid from the chamber. A traction unit for moving the cleaning unit along the cable to be cleaned is also known.
GP 2038212 A1 discloses an apparatus for painting which comprises a container formed of two halves hinged together, which has two aligned orifices through which the cable passes, an outlet orifice with an exchangeable die to determine coating thickness and an inlet orifice which is contained in a spigot extending from the container and including ring seals to prevent the coating material which is inside the container from rinsing or dripping out of the container. The cable is painted (soaked) by puffing it through the painting fluid inside the container wherein the amount of paint applied to the outside is limited by the diameter of the exchangeable die in the outlet orifice.
Caulking off voids, crevices and recesses in a wire rope between individual strands, bundles or single wires require mechanical force which can not be exceeded by the known apparatuses and is usually performed manually. For this purpose the sealing or caulking material is worked into cable interstices and can be built up to form planar surfaces between adjoining cables strands of a complete cable bundle. The caulking material is packed so as to avoid any bubbles or voids that could lead water into the interior of the cable. Instead of planar surfaces and completely filled voids between adjoining cable bundles and strands, it is also possible to form grooves following the voids between such cable bundles and strands to save caulking material. The whole process is performed more or less by hand and is labor-intensive and expensive.